It is known to provide air bag modules with vent openings through which inflation fluid may be discharged. When an occupant of a vehicle is positioned too close to the air bag module and is contacted by an inflating air bag, the vent openings enable some inflation fluid to be discharged from the air bag to atmosphere. The discharge of inflation fluid through the vent openings helps reduce the contact force between the inflating air bag and the occupant.
It is also known to associate a vent door with each vent opening of an air bag module. A tether connects the vent door to a portion of the air bag. When the air bag inflates to a predetermined location, the tether pulls the vent door to block a flow of inflation fluid through the vent opening. U.S. patent application Publication No. 2004/0051285 A1, which is assigned to the assignee of the present invention, discloses an air bag module having a vent door that is closed by a tether.
The interaction of the occupant and the air bag may result in a sudden increase in the inflation fluid pressure within the air bag. The increased inflation fluid pressure tends to force the vent door open. When the vent door opens, the flow of inflation fluid from the air bag through the vent opening increases. If not impeded, the increased flow of inflation fluid through the vent opening may result in the pressure within the air bag becoming lower than desired for the air bag to restrain the occupant.
An inflatable vehicle occupant protection apparatus that permits the contact force between the inflating air bag and an occupant to be reduced without unduly lowering the pressure within the air bag is desired.